It is known to provide an internal engine with a turbocharger to pressurize the air entering the engine so as to improve the performance of the engine in terms of torque output, emissions and combustion efficiency. A conventional turbocharger comprises a housing having a rotary compressor rotatably supported in a chamber at one end of the housing and a turbine rotatably supported in a chamber at an opposite end of the housing. The turbine and the compressor are driveably connected via a drive shaft supported by a central bearing part of the housing.
The turbine is arranged to receive exhaust gas from the engine and convert the kinetic energy of the exiting exhaust gas into a rotary driving torque that is supplied to the compressor. The compressor receives a supply of air, which may be ambient air or a combination of ambient air and recycled exhaust gas, compresses the supplied air and supplies the compressed air to the engine.
This arrangement produces a number of issues when packaging the turbocharger within an engine bay of a motor vehicle. Firstly, due to the large length of the ducts used to connect the turbocharger to the engine and the complexity of these ducts, compromises may have to be made. Secondly, a conventional turbocharger represents a relatively large mass that has to be supported on the engine. Thirdly, difficulties in packaging the turbocharger can lead to poor crash performance because the relatively solid turbocharger unit may occupy a space that may be impinged by other components during an impact. Finally, transfer of radiated heat from the engine to the cold compressor side components may occur due to the close proximity and close attachment of the hot turbine part of the turbocharger to the cold compressor part of the turbocharger, leading to heat transfer from the turbine to the compressor, which may result in a number of disadvantages. These disadvantages further include the requirement to use materials for the compressor side components having a better thermal resistance than would otherwise be required resulting in increased material cost. Also, higher charge temperatures from the compressor outlet due to this heating effect results in reduced engine efficiency due to the higher charge air inlet temperatures, reduced efficiency due to a need for increased post compressor cooling (intercooling) and thermal fatigue due to the temperature differential between the hot and cold sides of the turbocharger.
The inventors herein have identified the above issues and identified an approach by which the issues described above may be at least partly addressed. It is an object of the disclosure to provide a design for a bearing assembly for such a split turbocharger that aids assembly of the split turbocharger to the engine and is economical in construction.
According to a first aspect of the disclosure there is provided an example design for a turbocharger bearing assembly of a split turbocharger for an engine. The split turbocharger may have a compressor located on one side of a major structural component of the engine and a turbine located on an opposite side of the major structural component of the engine. The turbocharger bearing assembly comprises a bearing housing having a tubular body defining a bore for housing at least two spaced apart bearings, a drive shaft rotatably supported by the at least two spaced apart bearings, a compressor rotor forming part of the compressor located at one end of the drive shaft for rotation therewith and a turbine rotor forming part of the turbine located at an opposite end of the drive shaft for rotation therewith.
The tubular body may be sized to fit a bore in the major structural component used to mount the turbocharger bearing assembly on the engine. The bearing housing may have a flange located at one end of the tubular body for use in holding the bearing housing in position. The turbocharger bearing assembly may further comprise a housing for the turbine with an integral flange which may be used to secure the turbocharger bearing assembly to the major structural component of the engine.
The turbocharger bearing assembly may further comprise a housing for the compressor having an integral flange which may be used to secure the turbocharger bearing assembly to the major structural component of the engine. The major structural component may be a cylinder block of the engine. Alternatively, the major structural component may be one of a cylinder head of the engine, a crankcase of the engine and a bank of cylinders.
According to a second aspect of the disclosure, there is provided an engine having a crankshaft rotatable about a longitudinal axis of rotation and a split turbocharger comprising a compressor supplying charge air to at least one intake of the engine, a turbine connected to at least one exhaust of the engine and a drive shaft drivingly connecting the compressor to the turbine. The split turbocharger includes a turbocharger bearing assembly constructed in accordance with said first aspect of the disclosure supported by the major structural component of the engine so as to locate the compressor and turbine on opposite sides of the major structural component of the engine.
The compressor may comprise a compressor housing enclosing a working chamber and the compressor rotor may be located in the working chamber. The compressor housing may be mounted on a first longitudinal side of the major structural component of the engine. The turbine may comprise a turbine housing defining a working chamber and the turbine rotor may be located in the working chamber. The turbine housing may be mounted on a second longitudinal side of the major structural component of the engine. The major structural component of the engine may include one or more of a cylinder block, a crankcase, a cylinder head and a bank of cylinders.
In one example, the drive shaft may be arranged at substantially ninety degrees to the longitudinal axis of rotation of the crankshaft.
According to a third aspect of the disclosure a method is provided for assembling a split turbocharger to an engine. The method comprises assembling a drive shaft, a compressor rotor, a turbine rotor and at least two bearings to a tubular body of a bearing housing to form a turbocharger bearing assembly in accordance with said first aspect of the disclosure. The method further comprises rotating the drive shaft and the attached compressor and turbine rotors at a speed so as to balance the rotating parts and, after completion of the balancing step, fitting and securing the balanced turbocharger bearing assembly to the engine.
The turbocharger bearing assembly may comprise inserting plurality of bearings (at least two bearings) into a bore in the tubular bearing housing and engaging the drive shaft with the bearings so as to rotatably support the drive shaft. The turbocharger bearing assembly may further comprise fastening one of a compressor rotor and a turbine rotor to one end of the drive shaft before it is engaged with the bearings. The turbocharger bearing assembly may still further comprise fastening the other of the compressor rotor and the turbine rotor to an opposite end of the drive shaft after it has been engaged with the bearings.
The method for assembling a split turbocharger to an engine may further comprise fastening a compressor housing to a first side of the large structural component of the engine so as to cover the compressor rotor and form a compressor. The method may still further comprise fastening a turbine housing to a second side of the large structural component of the engine so as to cover the turbine rotor and form a turbine.
Fitting and securing the balanced turbocharger bearing assembly to the engine may comprise engaging the tubular body of the bearing housing with a cylindrical bore formed in the large structural part of the engine and fastening the tubular body in position in the bore.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.